1. Field of the Invention
The present invention relates to a manufacturing method, and more particularly to a manufacturing method for a composite coil spring.
2. Description of Related Art
A conventional coil spring is usually made of spring steel. The conventional coil spring uses the restitution force of the steel material for longitudinally absorbing the vibration. Consequently, the coil spring is widely used in a machine, a vehicle or a bicycle.
For example, in a bicycle, the main frame, the felly and all the elements of the bicycle are gradually altered for a light gravity to promote an exercise effect. Consequently, various alloys are used to make the main frame of the felly of the bicycle, such as aluminum alloy, magnesium alloy, titanium alloy and the like. Sometimes, the carbon fiber is also used. However, only the coil spring is still made of spring steel. The steel coil spring is heavy, and the steel coil spring may cause an aftershock when used in a bicycle for absorbing vibration.
Furthermore, the steel coil spring cannot absorb the vibration therefrom so that the absorber usually has a damping for absorbing the vibration form the steel coil spring. Consequently, the total weight of the absorber is raised.
For solving the above problem, some composite coil is developed. With reference to FIG. 10, the conventional composite coil spring (50) has two hook (51) respectively inwardly extending from two opposite ends of the composite coil spring (50). Consequently, a complicated mold is necessary for manufacturing the composite coil spring (50) with two hooks (51). The composite coil spring may be broken when opening the mold because the composite coil spring cannot load a great transformation rate due to the property thereof. Consequently, the manufacturing method of composite coil spring needs to be advantageously altered.
With reference to FIGS. 11 to 13, a column mold (60) is provided to manufacture the composite coil spring. The mold (60) has a continual spiral groove (61) defined in an outer periphery of the mold (60) for receiving the composite material (62). However, the mold is unique to the corresponding composite coil spring. Consequently, the manufacturer needs to prepare different molds for various composite coil springs. As a result, the manufacturing cost is raised due to the molds.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional manufacturing method for a composite coil spring.